The present invention relates to a double-socket electric lamp containing a low-voltage halogen light source, a transformer for the lamp, and a supporting arrangement of a secondary socket for receiving the double-socket electric lamp and the transformer.
An incandescent lamp has long been used for general indoor illuminants, and at present a halogen lamp is one of the most popular illuminants used for special purposes like a headlight in an automobile, a light source of a copying machine, and various illuminators for shops.
A 100 V-or-under low-voltage halogen lamp is more efficient than an ordinary incandescent lamp used at commercial voltage and deemed to be an energy-saving alternative to conventional incandescent lamps; also in the future halogen lamps will be one of the primary illuminants which will replace the incandescent lamp.
With the same electric power demanded, for example, a 12 V halogen lamp is higher in brightness by 40% or more than a 120 V incandescent lamp; and higher by 15% or more than a 100 V halogen lamp.
Besides, there are further advantages that the 12 V halogen lamp has a lifetime three times as long as that of the incandescent lamp because a thicker and shorter filament may be used compared with a filament used in a 120 V incandescent lamp and the inside of its glass bulb can be pressurized, and that adjustment of the light in the halogen lamp is facilitated because the halogen lamp is sized smaller, having a point light source, than the incandescent light.
However, the halogen lamp cannot be an alternative to the incandescent lamp until a transformer is used to reduce voltage from a 100 V to 120 V commercial voltage to a specified voltage (e.g., 12 V) suitable for use in the low-voltage halogen lamp. In addition to that, the halogen lamp is completely different in appearance from the ordinary incandescent lamp, and it is not well-known for general use.
Such a use of a low-voltage halogen lamp will be wide spread as an alternative of the incandescent lamp among consumers if it is shaped similar to the conventional incandescent lamp. For that purpose, it is desirable that its glass bulb and base are the same as those of the conventional incandescent lamp, and a double-socket electric lamp containing a low-voltage halogen light source is a general mode of the desirable alternative to the conventional incandescent lamp.
However, it is fully expected that a halogen lamp, shaped like the conventional incandescent lamp and used at a voltage as low as 12 V may be erroneously fitted directly into a conventional primary socket (120 V to 100 V) in the replacement of a bulb. In such a case, excessive voltage applied to the filament of the halogen lamp to cause an arc discharge, and an inner gas will rapidly expand. Consequently, the bulb explodes, and pieces of glass scattered by the explosion may hurt people therearound. In order to prevent an accident as stated above, something must be devised so that erroneous insertion of any double-socket electric lamp containing a low-voltage halogen light source into the primary socket will prevent any power supply to light the lamp.
Accordingly, it is an object of the present invention to provide a double-bulb electric lamp containing a low-voltage halogen light source which is not supplied with power nor lighted if it is erroneously fitted directly into a conventional primary socket in the replacement of a well known bulb.
It is another object of the present invention to provide a transformer having both a primary base to fit into a primary socket connected to a commercial power source and a secondary socket to fit on a base of a double-socket electric lamp containing a low-voltage halogen light source, for reducing commercial voltage to a voltage suitable for use in the double-socket electric halogen lamp.
It is still another object of the present invention to provide a fixing arrangement of the base of the double-socket electric lamp and the secondary socket of the transformer.